In this part of the lab, the characteristics of the pump diode for the target design laser (a CST-H-473 with a single TEC which maintains the temperature of the pump diode, amplifier, and SHG at the same value) are determined. These parameters (spectrum and wavelength characteristics) will be used as the input for a convolution simulation (in the same manner as described in section 5.7 of Laser Modeling) predicting the effect of diode temperature on laser output.
A CST-H-473 473nm DPSS laser is connected such that the original power supply operates the pump diode at a constant current and the external ILX LDC-5910C temperature controller controls the temperature of the single TEC which sets, among other parameters, the temperature of the pump diode.
Program the LDC-5910C controller with the correct Steinhart-Hart parameters (determined experimentally) for the laser as follows:
Set the temperature for 10C and enable the temperature controller. Next, switch the "DMOH" power supply on which will operate the diode at a constant pump current. Place an 808nm bandpass filter in the path of the output beam and direct the filtered output into a fiber and then into an OSA. Adjust the fiber until the spoectrum of the pump diode is seen around 808nm.
When the temperature of the TEC has stabilized, capture the spectrum of the pump diode as well as the peak wavelength of the spectrum. The spectrum must be captured at a resolution of 0.2nm - output values will be in units of dBm which may then be converted into linear units (e.g. mW).
Now, increase the amplifier temperature to 15C and observe the peak wavelength. Repeat at a pump diode temperature of 20C, 25C,and 30C - as temperature increases we expect to see the wavelength shift to longer values.
Hand In a WORD PROCESSED (not handwritten) lab assignment as follows. Put each question on a new page and ensure each page has a title "Question 1", "Question 2", etc. Also, please ensure the lab report is in a folder for submission (no loose pages).
To be done individually ...
Next, complete a simulation as per discussed in the lecture. To be realistic, you will be starting with nothing more than a graph of the absorption spectrum of the material from a research paper or a laser materials manufacturer. You must digitize the graph every 0.2nm (a time-consuming, but not overtly difficult process) to produce a table of data as a starting-point. Several free utilities exist on the web to perform this digitization (e.g. CurveSnapTM or some other graph digitizer program), alternately digitization is easy using a "paint" type program which displays the X/Y coordinates of a cursor in the graphic. If, for example, it was found that there are 90 pixels between any 2nm wavelengths our required 0.2nm measurements can be taken every 9 pixels. The Y-Axis (which reflects absorption) can be calibrated in a similar manner.
"Manual Digitization" means NO TWO STUDENTS will have the exact same results (!)
Complete a Simulation (using the convolution technique) predicting how pump diode wavelength shift will affect Nd:YAG DPSS output based solely on absorption of the pump radiation. Assume a diode with the spectrum as determined in the last lab. Produce the following: